Heat pumps can be useful in a variety of applications. For example, heat pumps can be used in plug-in hybrid vehicles and electric vehicles for heating the passenger compartment. Heat pumps are particularly useful because they are more efficient than other heating systems, assemblies, and devices, such as electric heaters. Energy saved with a heat pump can be used to extend the driving range of the vehicle using the onboard battery in electric mode.
In such heat pump systems, an accumulator has been conventionally used in a refrigerant loop, specifically, at a position between an inside heat exchanger (evaporator) and a compressor to control refrigerant conditions before entering the compressor. At an upstream side of the inside heat exchanger, an orifice or an electronic expansion valve (EXV) are typically used to regulate the refrigerant flow into the inside heat exchanger.
However, EXVs are generally expensive as compared to other expansion devices, whereas orifices are only optimized for one working condition which may lead to low cooling efficiency.